A great understanding of the Bible is the best defense to fighting evil. Remember Satan knows it so we better have a firm grasp on it. Remember it's our "sword". Jesus used it against the devil in Matthew 4:10,
"Away from me, Satan For it is written: Worship the Lord your God, and serve him only."
We tell Satan to leave us alone by being obedient to God. Even a small act of disobedience can open a crack to rebellion. Let's do life God's way - which is always the best way!